Automatic cutoff pump



July 369 lg a N. ASHTON AUTOMATIC CUTOFF PUMP Filed Jan. 27, 19444 2 Sheets-Sheet 1 NN mK www July 30, i946,

B. N. ASHTON 2,405,006

l AUTOMATIC CUTOFF PUMP Filed Jan.. 2'7", 1944 2 SheetsFSheet 2 ,firm/mim Patented July 30, 1946 AUTOMATIC CUTOFF PUMP Benjamin N. Ashton, Kingston, N. Y., assignor to Electrol Incorporated, Kingston, N. Y., a corporation of Delaware Application January 27, 1944, Serial No. 519,844

6 Claims.

This 'invention' relates to` improvements in pumps and relates more particularly to continuously driven pumps suitable for supplying liquid under pressure to hydraulic systems, such as, for example, the hydraulic vsystems used in aircraft for actuating retractable landing gear, folding wings, Wing flaps and the like.

The .pump f vsuch a hydraulic system usually is driven by the aircraft engine and it delivers liquidunder pressure at all times during the operation o. the engine. Inasmuch as the various hydraulically operated elements of the aircraft are actuated intermittently, the continuously supplied liquid under pressure must be diverted and recirculated in order to avoid excessive pressure in and damage to the hydraulic system.

' The liquid usually is V diverted andlrecirculated by means otadevice known as an unloading valve, whichfoperates -to bypass and return the liquid to a reservoir or tothe inlet of the pump when a predetermined pressure has been reached in the system.

An object of the present invention is to provide a pump that is responsive tov pressure in a hydraulic system and is capable of maintaining in the system a hydraulic pressure within a predetermined relatively narrow range. n

Another object of the invention is to provide a continuously driven pump that automatically ceases pumping when a predetermined liquid pressure is attainedin a hydraulic system, and resumes pumping upon a predetermined decrease of the pressure in the system.

A further object of the invention is to .provide a positive type of pump having continuously operated driving mechanism that is rendered ineiective -to actuate the pumping elements when the pressure in the system attains a predetermined maximum value and in which the pumping elements are rendered eiiective when the pressure in the system falls below a predetermined value.

Other objects of the invention will become apparent from the following description of typical forms of pumps embodying the present invention.

Pumps of the type embodying the present invention include pumping elements that are actuated by a drive mechanism that is coupled to and driven by a motor or an engine, for example, an aircraft engine. The pump is provided with a pressure-responsive mechanism that is actuated, upon attainment of a desired liquid pressure in an associated hydraulic system, to disconnect the drive mechanism completely from the pumping elements and maintain such a disconnected relationship until the pressure falls to a predetermined lower value.

More particularly, pumps of the type embodying the present invention may include a plurality of cooperating cylinders and pistons provided with suitable intake and discharge ports through which liquid may be drawn and discharged by the action of the pistons. The pistons may be reciprocated by means of a suitable drive mechanism such as a wobble plate that is actuated by means of a cam connected to and driven by the engine so that upon rotation of the cam, the pistons are successively advanced and retracted in their respective cylinders.

The wobble plate may be supported upon a piston member that is displaced by liquid pressure on one side thereof to disengage the wobble .plate from the cam. Liquid under pressure may be supplied to displace the piston by means of a valve mechanism that Yis shifted to an open position by a predetermined iiuid pressure in the hydraulic system and maintained in such open position until the pressure in the system drops a predetermined amount.

When the pressure in the system drops to a predetermined value, the valve mechanism is reset to discharge the liquid from behind the wobble plate piston to permit the wobble plate to engage `with the actuating cam and actuate the pump pistons.

Pumps of the type described generally above permit the unloading valve and associated conduits of prior systems to be eliminated inasmuch as the pump functions both as a pump and a pressure control mechanism.

For a better understanding of the present invention, reference may be had to the accompanying drawings in which Figure 1 is a view in longitudinal section of a typical form of a pump embodying the present nventiom Figure 2 is an end view of the pump; and

Figure 3 is an enlarged showing of a portion of the pressure-responsive valve of the pump.

The form of pump chosen to illustrate the invention includes a generally cylindrical housing I0 having a circumferential iiange 10a at one end thereof which abuts against a iiange Ila on the end of a generally cylindrical pump body portion ll. The pump body portion il, as illustrated, is

` provided with a plurality oi cylindrical bores I lb forming cylinders disposed around its periphery for receiving the cylindrical pistons l2. The pump body portion ll is also provided with a cylindrical recess llc forming another centrally 4051006 "iff: if...

ing element`.o'r'.valv}fplug I4 of the check valve may consist of a cup-shaped element havirne a flat cr disc-like valve face |4a that cooperates with a sealing ring |3b mounted in a groove |36 in the valve seat I3. Each of the valve pl-ugs I4 is normally urged toward its valveseat i3by means of a coil spring I5 interposed`bet'we`enthefback of the plug I4 and the end closure cap IS of the pump. When the plug 4 is seated, it engages the sealing ring I) 4and the face of the seat I3 inwardly of the ring I3 so that liquid pressure on the ring Ihand the plug I4 provides a strong and complete sl betweenthe plug I4 and theseatil. Y `.Asshown in Figure 24 the capl Il isgenerally diso'lle in plan and is provided ,with an annular axially'd'irectedflange |80?l that abuts against the aigeflIa ofthe pump body. vThe cap I6, the pump'body II' and the casing Il! may be secured together by means ef va plurality of bolts |1 passingA Ahrough the ,anges lila. |a and threaded intolth'e flange |641. l

j Escape of liquid from between the cap i6 vand the. flange IIa maybe prevented by means of a suitable rubbery sealing ring or gasket I8 receivedr in a groove IIe in the pump body and engagng the .flange IBG.' The pump cap I6 iS provided with ananfnular flange I Bb concentric with ih flange- Id and ani'uner concentric flange |5c forming, 'a cylin'd riapurposeto' be described. Thi flange 'lie re'eifedslessp'pcally inthe.. Cylindrical. recess IIC .G Lf the rmripbedy and sealedftetolby means'of al alingrin'gor gasket ISmountedin an annular groove ld 'in the nange |612; vThe annular space 2 9 between the flange ic and the ilange` Ib communicates with a discharge coupling Ie inthe cap I6. The coupling I lc is. adapted to be connected to a hydraulic .System so that the liquid forced from the cylinders lb through the check valves I3, |4 into the cavity 29 will be delivered directly to the hydraulic system for use'in actuating various elements ccnnected therewith.

l'h'e cylinder I Ic andthe space'2! within the flange Ib are'-conne-cted to an inlet coupling |6 in. the c'aplso that liquid from a reservoir or from the hydraulic system-:can ow into the cylinder itc and tothe intake ports lld.

:The pistons i2 are actuated'by means of a shaft 22'thatis driven by a motor or engine. The shaft is journaled in suitable anti-friction bearings 23 ne 24 that are mounted in a portion lob or the casing I3 of reduced diameter. In order to prevent leakage around the shaft, an oil seal 25 of conventional type may be interposed between the shaft and vthe portion lilb- Of the casing.

The inner' end of the shaft 22 is provided with accunter-balanced driving cam. For example, the shaft 22 may be provided with a counterbalancing member 26 having an eccentric and inclined arcuate recess 26a therein for receiving a roller-bearingdriving member 21.' The driving member 2 may include an outer' race 21a supported by a plurality lof tapered roller bearings 2lb and an inner race member flc. i The inner race Zic is clamped in the recess 26a onthe councylindrical portion 28a of the member 28 is received in a cylindrical cavity 28h coaxial with the recess 26a and similarly inclined at an angle to the axis of the shaft 22, with its flange 28h overlying the race 2Ic. The clamping member 28 may be retained in position by means of a bolt 23 threaded intothe. .member 2S. ,l

'he outer race'f2'la o f thebeariugzjpngages a wobble plate 3D thatismcunted forP rotation -and mutation on a ball member 3| mounted on a"shaft 32. The shaft 32 is slidably and rotatably mounted in the end of the pump body and extends axially of the cylindrical cavity ||c into fthfe Cylinder L59. @The ball 3| is mounted on a reduced portiongd of the shaft 32 and is retained thereon by means of a nut 33. The wobble plate includes a pair of telescopically assembled-disc-like members 30a and 3b having a ter-'balancedmember 2S by means o f'a flanged,

cup-shaped, clamping VAmember 28; The base or partially spherical aperture 35e therein for receiving the ball 3|. The members 373e and 30h have an intertting projection 3 Ild a nd reces s 38e andare connected by means of 'a series of 'bolts 35 which extend through overlapping portions of themembers 30a and 30D.

The wobble plate 30 is provided with a plurality of radially extending openings 301 for receiving the studs 36. Eachfof thestuds 36 is Provided with a reduced threaded portion 36a which is threaded into an internally threaded portion' of the bores 30f. ff

The studs 36 have Vgenerally spherical `heads 36h that are received in transverse openings I2a in the reduced end 'portions 1.21) ofthe pistons I2 so that nutation ofthe wobble plate '30 will cause the pistons |2 to reciprocatein the cylinders `||b. 'l'husjiupon'rotation of the shaft 22,` thedr'" 'ng ein 21 will-cause ,riut'auon'of the' wobbie' pratiavind ui'fbis'tohswiu be actuated to draw liquid into thecylinders Iflb and discharge the' liquid 'to' tlehydraulic 'system'.f

-Y lin-order t 'avoidwth' development 'of excessive pressures vby the system by the pump', the cap- |6 of the pump is provided with a valve mecha.- nism which controls the position of the `wobble plate 30 and renders theyistons I2 'effective'or ineffective to pump, depending upon the pressure in the system.

Ihe valve, together with the inlet port |6f and the discharge port |66 is disposed in a boss or a thickened portion I Bg on the cap I6 as shown in Flgures'l and 3 of the drawings. The boss |69 is provided with an axially extending bore Ih which terminates adjacent to thedischarge coupling IBe and is connected thereto by means of a small passage |612 Within the bore ISh'fis an annular valve seat 40 having a. tapered opening 40a communicating with a-cylind'rical passage 4Gb defining with the'upper face of the member 40 a sharp edged `'valve sea-t v llllcjf'oa ball valve 4|.

A sleeve member Y42 is ldisposed in the bore |671' andis maintained in spaced relationship tothe member 4D by means of an annular spacer meinber 43 of generally VL-shaped cross-section. 'v

The member 42 is provided with an enlarged internal bore 42a and a smaller passage 42h that forms with the lower face of the member 4 2- a sharp edged valve seat 42o for the ball "4|.-` -The diameter of the passage 42h is somewhat greater than the diameter of the passage '401). t

The ball 4| is normally-urged against the-valve seat 40o by means "of a plunger-"44which extends axially of the bore I Gg? and is provided with a reduced end portion 44a that -projects through thepassage 4 2?) andA engages th`e "'ball." The plunger 44 is also-provided with la-'ilamgeMb that .5 is engaged by a coil spring 45 extending between the llange 44h and a member 46 threaded into the outer end of the bore lIg for adjusting the prese sure exerted by the spring 45 on the ball 4I.

The members 43 and 42 are retained in xed relationship by means of a tubular sleeve 41 threaded into the bore IIh and retained in iixed position by means of a lock sleeve 48 also threaded into the bore IBh.

The spring adjusting member 45 is provided with an internal flange 46a that closely receives the plunger 44. A resilient sealing ring 49 is interposed between the flange 46a and a ring 50 against which the spring 45 bears to prevent leakage around the plunger 44. The adjusting member 46 may be locked in `adjusted position by means of a lock nut 4Gb threaded on its exterior and engaging a compressible gasket 45e received in a recess |67 at the end of the boss I6g.

The spacer member 43 is provided with one or ,A

more radially extending ports or passageways 43a that communicate with a groove 42d in the outer periphery of the member 42 and a passage 5| in the cap member I6 communicating with the space within the tubular member I6c in the interior of the cap I6.

The interior of the cylinder IIc and the space between the flanges I6b and I6c are connected with the interior of the sleeves 41 and 42 by means of a passage 52 and a passage 41a through the sleeve 41.

The valve construction and passages described above are utilized to actuate a piston 53 that is fixed to and carried by the shaft 32 and movable axially of the cylinder IIc. The area of a face of the piston 53 is greater than the combined areas of the faces of the pistons I2. The piston 53 is sealed to the cylinder I Ic by means of a rubber sealing ring 53a supported in a peripheral groove 531) in the piston. The piston 53 and the shaft 32 are normally urged toward the right by means of the spring 54 that engages the piston 53 and the cap member I6 and encircles the shaft 32. The shaft 32 extends beyond the piston 53 and is reduced in size to form a piston 32h that is slidably received within the tubular rmember I6c. 'Ihe piston 3217 is maintained in liquid tight relation to the member I6c by means of a rubber sealing ring 54 and is provided with an axial bore 32o that intersects an inclined passage 32d opening to the exterior of the shaft 32 at the right hand side of the piston 53 so that liquid flowing through the bores 32e and 32d will be discharged into the space between the right hand end of the cylinder I Ic and the piston 53. A suitable sealing ring or gasket 55 may be interposed between the cylinder IIc and the casing I0 and encircling the shaft 32 to prevent leakage.

In operation, with the shaft 22 driven continuously, the wobble plate 30 is nutated to reciprocate the pistons I2 in their respective cylinders IIb.v Liquid is supplied through the couplingf I6f to the cylinder IIc and is drawn into the cylinders I Ib through the ports IId by means of the pistons I2. As the pistons advance past the inlet ports IId, the liquid is forced out through the check valves I3 and I4 into the space 20 and` thence to the discharge coupling ISe. As the pistons retract, the check valves I3, I4 close and a reduced pressure is created in the cylinders, thereby drawing the liquid into the cylinders IId for subsequent discharge. As the pump continues to operate, the pressure of the liquid in the system is increased to a predetermined value, for example, 1090 lbs. per

6 square inch. When the pressure in the system attains the desired value, the back pressure in the system, acting through the passage |61' will displace the ball 4I from the valve seat 40e against the action of the spring 45. The spring 45 is adjusted or selected so that it will retain the ball 4I on the valve seat 40o until the desired pressure is attained in the system. When this pressure is attained, the spring 45 is compressed and the ball 4I is displaced upwardly as viewed in Figure 1, urging the ball against the valve seat 42o. Inasmuch as this valve seat is of a greater diameter than the valve seat 40o, the effect of the pressure on the ball 4I is considerably increased. Thus the diameter of the seat 42e may be such that the pressure in the systemmust drop to 900 lbs. per square inch before the spring 45 can return the ball 4I to the seat 40e.

With the ball in its displaced position, liquid flows through the passage 43a, the groove 42d and the passage 5I into the Space between the end of the plunger 32h and the annular flange IEc. The liquid also flows through the passage 32o and 32d behind the piston 53, thereby urging the piston to the left against the action of the spring 54 and moving the wobble plate 30 out of engagement with the drive member 21. In the form of the invention illustrated, the wobble plate 30 will engage the end of the pump body portion II and will be rocked into a position substantially perpendicular to the axis of the shaft 32. This movement of the wobble plate advances all of the pistons I2 to the left where they are retained so long as the ballv 4I is displaced from the seat 40C.

When the pressure at the discharge port or coupling |66 decreases sufciently, the spring 45 and plunger 44 displace the ball from the valve seat 42o and return it tc engagement with the seat 400. In this position, the liquid behind the piston 53 flows through the passages 32d, 32o, the passage 5I, the passage 43a, the port 42h, through the ports 41a and 52 and into the cylinder IIc. This releases the pressure behind the piston 53 and permits the spring 54 to move the piston to the right, thereby reengaging the wobble lplate 39 with the driving mechanism 21 and causing a resumption of the pumping operation.

The above described construction, therefore, provides a pump which automatically cuts off at a predetermined pressure and resumes pumping at a lower predetermined pressure, thereby doing away with the necessity of providing a separate unloading valve for a hydraulic system, while assuring that the pressure in the hydraulic system will remain within a. desired operating range.

While the invention has been described with reference to a piston type of pump, it will be understood that it may be utilized in conjunction with other types of positive acting pumps. Therefore, the form of the invention as described above should be considered as illustrative and not as limiting the scope of the following claims.

I claim:

1. An automatic cut-off pump comprising at least one pump cylinder having an inlet and an outlet, a piston reciprocable in said cylinder to draw liquid into said cylinder through said inlet and discharge liquid through said outlet, rotary driving means, a wobble plate actuated by said rotary driving means for reciprocating said piston, and means responsive `to va predetermined liquid pressure :at .the outlet of said cylinder for shifting said wobble plate out of engagement with said rotar-y driving means to render that `latter ineffective to reciprocate said piston, said `pressure .responsive'means being responsive .to a lower pressure than said predetermined pressure to shiftsaid wobble plate into engagement with said rotary driving means to render the latter effective 4to reciprocate said piston.

.2. An automatic .out-off pump comprising a `cylinder having an 'in-let 'and an outlet, a piston reciprocable in said cylinder to dra-w liquid linto said cylinder through ysaid inlet and .discharge liquid from `said outlet under pressure, Y.a ymtary cam member ladjacent ,one end of said piston, a power transmitting element engaging said piston and said cam member for reciprocating said piston in response to rotation of said cam, and means responsive to a predetermined liquid pressure at said outlet for moving ysaid power transmitting element .out of .engagement Ywith said cani to terminate reciprocation .of said piston.

'3. automatic cut-ofi ,pump Icomprising a 'pump body having a plurality of substantially @parallel cylinders radially spaced about the axis of said body, pistons reciproca-ble -in said cylinders for `drawing liquid into -said cylinders and discharging .'liquid yto a ihydraulic system, a driving -memberhaving a vface inclined tothe axes of lsaid body and said cylinders, and adjacent to Ithe end of each of said pistons, a wobble plate operated by said .member interposed between said end of each piston and said driving member, means .urging said end of each piston'toward said driving member, means for rotating said driving `member .and .said body relatively to cause nutation .of said wobble plate to reciprocate said pistons'in said cylinders, .and mea-ns responsive to a tpredetermined pressure tin said hydraulic system for shifting said wobble plate to move said ends vof said .pistons :into Aa plane substantially perpendicular to theaxisof said -body to .render rela- 4tive rotation 'of said body and said idriving mem- :ber ineffective to reciprocate said pistons.

4.,An :automatic vcutof pump comprising at Vleast one 'cylinder having an inlet .and an outlet, a :piston reciprdcable :in said .cylinder 'for ,ad-mitting .liquid 4through said inlet 'into said cylinder and discharging liquid under pressure through .said .'.outlet, .a rotatable Vmember having a face vinclined-to theaXis-oi said cylinder, a'wobb-le plate connected `to said piston, ymeans supporting and urging said plate .against said inclined face to reciprocate .said .piston .upon rotation .of said member, .and means responsive to a predetermined pressure at said outlet for yshifting vsaid wobble plateout of engagement with said rotatable member, said means retaining said wobble .plate in shifted position until the `pressure in saidsystem .drops to ya predetermined `lower value.

5. An automatic cut-.oli pump .comprising at least one .cylinder .having an inlet .and .an outlet, a ,piston ,reciprooable in said .cylinder for `admitting liquid through ,said inlet into said .cylinder and discharging liquid under 4pressure through said outlet, a rotatable member having .a face .rinclined to the axis .of .said cylinder, a wobble plate connected to .said piston, .means supporting .and urgingsa'id plate against said inclined face to reciprocate said piston upon rotation of said meinber, a piston on said supporting and urging means, a .cylinder for said last-mentioned piston, a valve having a first port connected with said outlet .and the last-,mentioned cylinder, a second port connected with said last-.mentioned cylinder and said inlet, a Vvalve member for sealing either of -said ports and means normally urging said valve member into said first port, whereby displacement of said valve member from said rst port by liquid pressure atsaid outlet admits .liquid .to .said last-mentioned cylinder to `displace said wobble plate from engagement with said inclined face, and displacement of said valve memberirom said second -port discharges liquid from said vlastmentioned cylinder to Areengage said wobble plate with said inclined face.

v6. An automatic .cut-olf pump comprising .a pump body having a substantially centrally .dis- .posed cylinder and a plurality .of substantially parallel smaller cylinders disposed radially outwardly .of said centrally disposed cylinder, each having an inlet and an outlet, a piston in each of said smaller cylinders, a larger piston in said centrally disposed cylinder, a Vshaft projecting from said larger piston, 4a wobble-plate mounted for nutation on said shaft and connected to .each of the pistons in said smaller cylinders, a rotatable -driving member having an inclined face adjacent to said wobble plate for nutating the latter to reciprocate said .pistons in said smaller cylin ders, means urging .said wobble-plate and large 1 Vpiston toward said .driving member, a two-position valve having -a rst port vconnecting said centrallydisposed cylinder with the outletsvof said smallerl .cylinders to deliver liquid under pressure yto displace said larger piston in Opposition to sai-d Avurging means, a second larger port connecting the centrally `disposed cylinder with said inlets to discharge liquid from said .centrally disposed ;cylinder to said inlets, a valve member .for sealing said Iports alternately, and means nor-- mally urging said valve member intosealing relation with said yiirst port.

BENJAMIN N. ASHTON. 

